Tach Boards Failing after 5 minutes run time

I've got the same issue, but my upgrade ran perfectly at any speed, but 5 minutes later it ran away? PS there was no excessive current draw so this does not make sense!

Alan

Both of these recent PS-32 purchases?  If so I would call Mike.  It sounds like a top board issue with the current limiting resistor possibly.  The return line requires a 181 ohm resistor to limit current to tach.  If that resistor is wrong, or damage too much current to tach reader.  G

thanks, GGG thanks really appreciate the help! sincerely appreciate the help!

Alan

@GGG posted:

Both of these recent PS-32 purchases?  If so I would call Mike.  It sounds like a top board issue with the current limiting resistor possibly.  The return line requires a 181 ohm resistor to limit current to tach.  If that resistor is wrong, or damage too much current to tach reader.  G

How did they manage to screw that up?

Gunrunner when is MTH not screwing something up!  they can't even get the right color wires on harnesses! Alan

Update: The PS32 boards were bought in 2023. I have a few 3v stackers to try another. I noticed a 10 k 1/8 Watt resistor in series with the Output line from Tach to the 7 pin Conn. on the stacker. Because that resistor is not shown on drawings I have from MTH tech school (2010), I jumpered around it, and no benefit. On further testing, if you turn power off a while it will run correctly for a few minutes. I am going to try another board next.

The 10 K is in the older 5V harness and some of the 3V as carry over for chuff in neutral.  Was on the orange signal wire.  The 181 ohm is in the blue return line. PCB ground.  This is the current limiter.  I just checked one of my new Stackers and the resistor is 181.

So frankly I do not know what is going on in your set up or Alans.  Is this a repair on a MUX engine?  If so, the blue tach wire is not returned via the 7 pin where the 181 ohm resistor is.  Instead the MUX board has it and tach return is via mux.  So maybe a bad mux board.

I have only seen a bad 181 resistor a few time.  Not common at all.   Also your run away could be bad wiring that is intermittent.   G

This engine is a MTH Tinplate (Lionel Corp Tinplate). The Blue wire from tach goes to Pin 1 on the 7 pin. The gray wire from Tach goes to pin 4 on the 4 pin, and the orange wire goes to Pin 2 on the 7 pin via 10k resistor. There is no wire in the Blue wire from the tether.

Tinplate doesn’t use MUX boards.  Which tinplate?  Electric, steam with board in loco or tender?

Standard gauge or O gauge.  There should be no reason the PS-32 board is damaging the tach reader.  You said you replaced tach reader, did you replace with PS-2 or are you trying to use a PS-3 tach reader?   G

Hello GGG and thanks for all this help. This is not a MUX engine. I measure 182.2 ohms from pin 1 on the 7 pin conn. (blue return from Tach) to pin 1 on the 12 pin (PCB Ground). So the resistor is there on the board. I don't think the Tach's are being destroyed, as they do work for a while. I swapped out the board set, and ran it with the base sound file, probed the wiring while running slow as expected. Ran for 12 minutes and ran away again. I tried moving the tether around while it was under test, but it didn't run away, but finally did while I was no longer sitting next to the track. Next I will put the engine on my stationary roller track and test while checking wires.

Oh, and this is an O gauge Baby Blue Comet. No Mux boards.

And the tach sensor is a PS2 as I asked the MTH folks and that's what they said should work with the PS3/2 stackers. I have used the same Tach now for 4 tests, and the last test at 12 min was the longest, so I was wrong about the tach being destroyed.

I have only replaced a handful of tach sensors over time, they do fail, but really not that often.  Since the PS3/2 board is meant to be a drop-in replacement for the older PS/2 boards, both 3V and 5V, it does obviously have to use the PS/2 tach sensor.

Check the pin joints on the Engine PCB and swap in a new tether.  Sound like intermittent wire issue.  G

I've tried 3 different tethers with the same results, I guess the next step would be to monitor the tach board current draw while the engine is running!?

Alan

What are you working on Alan, your issue is different than the original posters.  Need more details. 

Update: I have proved the wiring is the problem. Ran a set of wires direct from Tach Board to the PS 3/2 board, soldering on back side of board to the Connector pins as needed. Ran well over 1 hour without running away. I will isolate now to the bad wire. I am bypassing the 10k resistor in doing this, but seems to be okay not using that.

GGG John said "replaced a burned up PS2.0 3-volt board set with a PS 3/2 stacker board set." the only difference is I'm doing a upgrade PS 3 steam Williams engine!

I have the exact same board set with the same conditions, and issues as stated, George any new ideas! Sincerely thanks GGG

P.S . GGG I also contacted Don at MTH and he suggested asking you about this issue!

Alan

I have not seen this specific issue on PS-32 boards.  Johns issue was his wiring apparently.  Are you sure tach is not touching shell?  Tach gap right to flywheel?  Good tach tape?  Are you sure the readers are burning up?  Johns were not.  Take board out and run in your PS-2 test set and see what happens.  G

I've at least 30 of the steam upgrades, and I've never had any issues with the tach sensor board, so I'd have to suspect wiring somewhere.

GGG the tach board is not touching the case only the plastic holder, I'll try the board again on the PS 2 test fixture and get back to you! also the gap is correct on the tach reader and the tape is clear and in good shape! also no I'm the sure the tach boards are bad because after you shut it down and wait a few minutes it will run again for 5 minutes again! then the same systems start again!

Alan

@Alan Mancus posted:

I'm the sure the tach boards are bad because after you shut it down and wait a few minutes it will run again for 5 minutes again! then the same systems start again!

It sure sounds like the tach boards are NOT bad if it runs after shutting it down for a spell.  In addition, multiple tach boards simply do not go bad in a batch like that, the odds are astronomical against it!!

That does sound like a board issue after it heats up.  Is the flywheel loose?  Of course that wouldn't take 5 mins to happen.  I would go back to MTH and make them test that board.  If it repeats the symptom on your test set it has to be the board.  G

Just to close out my problem with which I started this post, My problem was apparently in the locomotive 10 pin bulkhead connector. I resoldered the Tach Output pin and wire connections, and my problem never came back. I also fell into a trap with using the default code files in the PS 3/2 stacker set that are loaded at the factory, which allowed the engine to smoke but like a diesel, not a steamer, then I failed to load the chain files for a standard Steam w/smoke. After I fixed that, all is good. Thanks for all the advice.

Glad that was all it was.  Correct flash code and the engine wiring are all critical.  Also, it is the pins to pcb that need to be resoldered.  I see plenty of cases where customers tell me the resoldered engine pcb and it still has issues.  They resolder wires to pad, but that was not the issue.  The solder at pins to pcb crack.  G